(1) Field of the Invention
This invention relates to fight sources for projectors, in particular to light sources using ultraviolet light sources.
(2) Brief description of Related Art
A prior art light source for a projector is shown in FIG. 1, as described in the co-pending U.S. patent application Ser. No. 10/139,780
FIG. 1 shows the basic unit of a matrix of light emitting diodes (LED) to form the light source cell of a color picture projector. Three primary color red R), green(G), blue (B) LED packages are mounted in a matrix formation in a module as a three-gun light emitting light source. The R, G, B LEDs 10R, 10G, 10B emit individually light beams through three transmissive liquid crystal plates 12R, 12G, 12B and then through three lens system 14R, 14G, 14B, respectively. The transmission through the liquid crystal plates are each controllable. The lens system 14R, 14G and 14B are tilted to focus the three R, G, B light beams to the spot on the projection picture screen 16 and form a single dot to the viewer. The appearance is the same as the dot-matrix display on an ordinary computer monitor. The transmissions through the crystal liquid plates 12R, 12G, 12B vary with time to form a motion picture.
In this prior art, three different kinds of LEDs are needed. The cost is high both initially and during maintenance.
An object of this invention is to reduce the cost of light sources for a projection system. Another object is to reduce the maintenance cost of the light sources.
These objects are achieved by replacing the different color light sources with ultraviolet (UV) light emitting diodes. These UV are used to activate red, green and blue fluorescent plates to emit red, green and blue light. The different color lights are transmitted through a programmable liquid crystal plate or reflected by a digital-micro-device (DMD)for a projector. The different color transmitted or reflected light beams can be projected simultaneously or sequentially.